Spreadsheet software - many options: Google docs has a free spreadsheet in the browser, and now Microsoft has a free browser one too with skydive (yay competition!). There's also the free open source Libre Office application. And the famous Microsoft Excel spreadsheet products which work great and are kind of expensive. Any of these will work for all our examples and homeworks.

Aside: How to Invent The Future

Who Makes Great Software?

The creators of the spreadsheet knew finance math and paper spreadsheet practices

They also knew computers

Lesson: knowing the problem domain may be the key to creating great software
-Know what problem to solve
-Know how users look at the problem
-Know the user's priorities
-as opposed to CS experts coming into a domain they don't know

e.g. Perhaps a working biologist will think up the next great biology program, not a CS person dabbling in biology

Hidden agenda: everyone should know a little CS

Monster Example

Monster example spreadsheet in google docs. Below we'll use this as a running first example. (consider: control-click .. open in new tab)

To edit above (or any of our spreadsheets): either (a) In google docs: File > Make Copy to edit. or (b) File > Download As > .xlsx file, and then edit using any program.

Experiment: click on a cell, note its "address" B1 or whatever, type in a word or number

2. Columns of Numbers

Very common to have a few columns of numbers

e.g. the Red Castle and Blue Castle numbers here

These are just raw numbers without computation

3. Add Computation: sum()

Compute the total number of monsters in the blue castle

Click on the B8 cell, a couple rows below the last blue castle number

Good practice: leave a blank row between the raw numbers and your computed cell

Type in the following "formula" (with the equal sign): =sum(B1:B6)

The equal sign = at the start means this cell is computed from other cells

The sum() adds up all the numbers in a range of cells

The b1:b6 means the whole vertical group of cells from B1 down through B6 (lowercase or uppercase work the same e.g. b1 or B1 )

Type in "Total Count" in the cell to the left (A8) to serve as a label

Famous Reinhart/Rogoff bug - wrong cell range in formula
-Spreadsheet error made "austerity" look like a better strategy than it is
-Admirable of them to share their data with "reproduce" scientists
-Science is based on published methods and reproduction of results

Spreadsheet Editing Tricks

When you change a number up above, the sum is automatically updated

Once you type in the =sum(...) in the cell, it displays as the computed sum number (28 in this case)

Single-click - edit up above

Double-click - edit in the cell

Esc key to cancel out of editing - a life saver
-somehow I always find myself editing a cell I did not want to edit

Color shows cell-dependency (vs. wrong-cells bug)

Click-drag alternative to typing "b1:b6"

Using =sum() to add up a bunch of numbers is super common

From the headlines: Reinhart and Rogoff had a popular economics paper supporting austerity, but it had a significant spreadsheet bug. Essentially they wrote something like sum(a1:a8) when they intended (a1:a11), so they left out some numbers. This bug was significant in the paper's results. The subsequent history of the great recession has shown austerity to be a bad idea. Note when you double-click a cell, it shows you what it depends on to help avoid this sort of bug. It's amusing that such high level research can have ordinary bugs just like the rest of us, although of course this should be no surprise. Bugs are a common part of software.

4. Add Computation: + - * /

Suppose every monster pays $100 per night and we want to compute the $ income per night, i.e. count*100

We can write an arithmetic formula like =B1 * B2 in a cell to compute a number based on the values of other cells

Click the B9 cell just below the sum

Type in the formula (with the equal sign): =B8 * 100

Probably the easiest way to edit an existing formula such as in B8 and B9 is double clicking the cell

Trick: while typing in the formula, instead of typing "B8", just click the cell you mean

Type in "Total $/night" as a label to the left

This is similar to the earlier sum() computation, but with basic + - * / type arithmetic

5. Magic: Fill Right

Once you have the B8 and B9 formulas working the way you want, how to replicate them for the Red Castle?

Easy!

Click on B8 and drag right to highlight C8

Type ctrl-R, the Fill Right command .. this is extreme magic

Fill Right duplicates the formula over to the right

Filling from column B to C

Formula in column C updated to use C numbers

Click B and C computed cells to check this

Do Fill Right for the Total $/night formula as well

6. Chart Magic

Finally we'll add a chart

Click on A1 (the upper left enclosing the whole thing)
..drag down to the lower right of the data (C6)

Here just using the column titles and data

Not the computed cells

Select Insert Chart

There are many types of chart available

Experiment with bar vs. line chart, or maybe add a title, resize it a bit

Chart option checkbox:
-"Use column A as labels"
-Check this is each row has its own label

Position the chart below all the numbers

Notice: changing a number updates the chart

Making pretty charts with your data is pretty easy

Here's a picture of it in done form:

Compute average with average(a1:a10)

Above sum(a1:a10) computes the total sum of range of of numbers

Similarly, average(a1:a10) compute the mean average of range of numbers

sum() and average() are probably the two most commonly used functions

2. Cell Phone Example - You Try It

Say we are studying how many times each person check's their cell phone per day